A Case Study of Web Services Orchestration

Abstract

Recently the term Web Services Orchestration has been introduced to address composition and coordination of Web Services. Several languages to describe orchestration for business processes have been presented and many of them use concepts such as long-running transactions and compensations to cope with error handling. WS-BPEL is currently the best suited in this field. However, its complexity hinders rigorous treatment. In this paper we address the notion of orchestration from a formal point of view, with particular attention to transactions and compensations. In particular, we discuss webπ∞ an untimed subcalculus of webπ [15] which is a simple and conservative extension of the π-calculus. We introduce it as a theoretical and foundational model for Web Services coordination. We simplify some semantical and pragmatical aspects, in particular regarding temporization, gaining a better understanding of the fundamental issues. To discuss the usefulness of the language we consider a case study: we formalize an e-commerce transactional scenario drawing on a case presented in our previous work [12].